Dark themes for readability
Many people underestimate a good theme, dismissing it outright as flair or pure vanity. This is wrong – a good theme is a good user experience – it increases readability and makes you notice errors, keywords and all the syntax spice intuitively, without having to think about it. There are several benefits to using dark themes:

when looking at a bright display, your eyes get fatigued faster, especially at night (which is when most programmers tend to do their work). On dark displays, instead of focusing on the entire bright screen and trying to discern holes in it (darkness – letters), your eyes are immediately drawn to the bright parts – the text, ignoring the background altogether.

I subjectively claim that colors are easier to notice when on darker backgrounds. Naturally, this means the colors should have a decent, but not too strong contrast to the background

It’s a known fact that blue light from self-lit displays suppresses melatonin, which in turn disrupts your sleep patterns. If you find yourself having difficulty falling asleep after a 4AM coding session despite feeling utterly obliterated by fatigue, try a darker theme and exposing yourself to less light in general when working at night.

Things to look for in a theme are mid-range contrasts. Avoid absolutes – the background shouldn’t be pure black, and the text shouldn’t be pure white/red/green/orange. These sharp contrasts confuse and strain the eye just as much as having an all-white background and all-dark text does. Instead, look for pastel, smokey colors. Likewise, increasing the font is usually a good idea, if the theme’s default is tiny. The eyes strain when reading too small letters, and if the spacing isn’t good enough either, you’ll have a hard time reading anything without welcoming a headache. Two of my suggestions for darker themes are Darcula, which comes built into PhpStorm, and Solarized.